1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly, to an image forming apparatus and a developing unit thereof that is equipped with sealing members to prevent a developer from leaking.
2. Description of the Related Art
Generally, an image forming apparatus is an apparatus that prints an image on a printing medium, e.g., paper, according to an inputted image signal. As one example of the image forming apparatus, an electrophotographic image forming apparatus is configured such that a light beam is scanned to a photosensitive member charged with an electric potential to form an electrostatic latent image on the outer peripheral surface of the photosensitive member, the electrostatic latent image is developed into a visible image by adhering a developer onto the electrostatic latent image, and the visible image is transferred and fixed onto paper.
A developing unit of an image forming apparatus supplies a developer stored therein to a photosensitive member to develop an electrostatic latent image of the photosensitive member. FIG. 1 is a sectional view illustrating components of a conventional developing unit, and FIG. 2 is a view seen in the F direction of FIG. 1. As illustrated in FIGS. 1 and 2, the conventional developing unit includes a developer feeding member 2 which supplies a developer to a photosensitive member 1, contact members 3 which are rotatably mounted to both ends of a rotating shaft 2a of the developer feeding member 2 and rotate while contacting the outer peripheral surface of the photosensitive member 1, and a sealing device 4 which prevents the developer inside the developing unit from leaking outside.
The contact member 3 has an outer diameter larger than the developer feeding member 2. Accordingly, a development gap G is defined between the developer feeding member 2 and the photosensitive member 1. In the process of adhering the developer to the electrostatic latent image of the photosensitive member 1 to develop the electrostatic image to the visible image, it is important to maintain a constant development gap G to secure uniform and stable image quality.
The sealing device 4 includes first sealing members 5 which are provided on both ends of the developer feeding member 2 to prevent the developer from leaking through side portions of the developer feeding member 2, and a second sealing member 6 which is provided to contact a bottom of the developer feeding member 2 to prevent the developer from leaking through a lower portion of the developer feeding member 2. The second sealing member 6 is formed as a film type. One end portion of the second sealing member 6 contacts a housing 7 of the developing unit, and the other end portion of the second sealing member 6 contacts the outer peripheral surface of the developer feeding member 2 due to its own elasticity.
However, in the above conventional developing unit, because the second sealing member 6 has a length similar to the developer feeding member 2 in the axial direction, both ends of the second sealing member 6 interfere with the first sealing members 5 which seal the side portions of the developer feeding member 2. Because the adhesive force at both ends of the second sealing member 6 adhering to the housing 7 is weakest, the interference between both ends of the second sealing member 6 and the first sealing members 5 may cause f the second sealing member 6 to separate from the housing 7 when the developer feeding member 2 rotates.
Further, the sealing device 4 of the conventional developing unit cannot perfectly prevent leakage of the developer. If the developer leaks, the scattered developer contaminates the contact member 3 and forms a foreign substance layer between the contact member 3 and the photosensitive member 1. If the contact member 3 is contaminated, the development gap G between the developer feeding member 2 and the photosensitive member 1 is not kept constant, and it causes image quality degradation.
To solve this problem, Korean Patent Registration No. 460,995 discloses a foreign substance removing device for an image forming apparatus that removes a foreign substance layer adhering to a development gap maintaining member. The disclosed foreign substance removing device is configured to mount a blade for removing foreign substances, an elastic supporting member which elastically biases the blade, and a fixing frame for supporting the blade and the elastic supporting member inside the developing unit. However, the structure of this developing unit needs be improved, for example, by reducing its complexity to reduce manufacturing costs.